Refining Audio Setup

So I've done alot of thinking on my pc upgrade and audio remains a bit of a questio mark despite some previous advice on here.

I think I've started to narrow down what I'm looking for and the audio solution for headphones isn't what I first thought it might be.

Would appreciate a bit more advice if possible and atm I'm looking at the DT990 and the Pro 900.

My preference is Gaming > Music > Movies

I'm using an Asus STX Essence to drive the headphones and first and foremost I really want to enjoy the best audio stage for BF3 to maximise immersion followed closely by music listening of varied genres.

I do have the consideration that sound leakage and open phones could be a problem as I'm shift based so 90% of my gaming is done at night and whilst I'm in the living room with the door shut, the bedroom is right behind it and I don't want to wake the wife!

This seems to push me towards the Pro 900 which seems like a really nice set of cans but I'd appreciate some views as from what I read the DT990 has the better soundstage and is just as capable bass wise.

Price range is no more than £300.

I've spent a few nights reading up on this and it really is confusing especially where the STX is concerned.

I was settled on the DT990 but further reading now has me fluctuating between:

DT880 / 600 - Seems superb but alot of advice says the STX can't drive it and requires an external amp. I'd be fine buying something within reason but this is way outside my knowledge range and I just want something to work.

AKG702 - Again gets a great review but not so sure it'd have the bass I want to really be immersive with explosions etc

HD598 - My original choice but again might lack bass

Everytime I think I have a solid choice I'm suddenly back to square one.

I'm ok to upgrade the op amps on the STX but I just want to find a set that gives immersive bass in games like BF3 and movies. The DT880 does seem to be the right type of headset but I'm just left more confused the deeper I read into it.